Improvements to the cutting heads of dry shaving apparatus



June: 18,v 1963 B. FUTTERER 3,093,899

IMPROVEMENTS TO THE CUTTING H S 0F D SHAVING APPARA'I S led Aug. l2, l9

5 INVENTOR BODO FUTTERER BY% /%WM $25M ATTORNEYI'S United States Patent 3,093,899 IMPROVEMENTS TO THE CUTTING HEADS F DRY SHAVING APPARATUSES Bodo Futterer, Langen, Germany, assignor, by memo assignments, to Braun Aktiengeselischaft, Frankfurt am Main, Germany Filed Aug. 12, 1960, Ser. No. 49,372 Claims priority, application Germany Aug. 19, 1959 2 Claims. (Cl. 30-43) The invention relates to dry shaving apparatuses and concerns the construction of the cutting plates or perforated plates used therein. A plate of this type is usual- 13 fixed over the movable cutting arrangement of the cutting system, and is then referred to as the cutting guide plate. It can also be used as the movable inner cutter part and is then known as the cutter plate.

The parameters determining the cutting efficiency of a dry shaving apparatus are the shape and size of the holes, the arrangement and number of the holes, the width of the Web portions and the thickness of the plate. By the term cutting efficiency is understood the sum of the qualities required of the apparatus by the user or observed in the apparatus, for example in comparative tests; these qualities are length, closeness and smoothness of the shave i.e. the cutting efliciency on the one hand and, on the other hand, the effects on the skin (irritating effects or beneficial effects).

There have been a number of tests to determine these numerous parameters in such a way that the shaving efficiency will be at an optimum. Some of these parameters can be replaced by others thus the hole size and the width of the web portions can be replaced by thickness of the plate which in its turn is determined by the mutually counteracting requirements in the material in respect of flexibility and mechanical strength; similarly the number of holes can be replaced by the hole shape and arrangement as well as by the width of the web portions for a given total surface area.

In the case of known cutting guide plates the circular hole shape preponderates because the circular hole represents the most favourable contour for uniform penetration from all directions of the hairs of the beard and also for uniform protrusion of the skin against the cutting part. This hole shape is however unfavourable for catching the longer hairs and is also disadvantageous because the inoperative or dead gusset formed between the holes necessarily worsens the opening ratio, this latter term indicating the ratio of the total useful surface area, of the openings through which the hairs pass, to the residual intermediate or web surface. Both increase the shaving time.

In this connection the arrangement is substantially better whereby a plurality of mutually overlapping holes are aligned to form longitudinal holes having sickle shaped cutting edges. This hole shape at the same time permits a larger hole size, without the plates containing them having to be thicker or the skin being adversely afiected in shaving.

On the other hand tetragonal or rectangular holes have also been used in order to improve the opening ratio; these however did not constitute a noteworthy step forward as against circular holes.

Thus in both these cases the influence of the hole shape on the shaving or cutting performance is not taken into consideration. The hole shape together with the direction of the cutting movement determine the configuration of the cutting edges, and so also the efficiency of the cut obtained. It has been found in the course of very thorough tests that holes with wedge-shaped cutting edges provide a shave which is unusually soft and yet close and smooth, and on skin and beards of widely different type. It was also observed in these tests that the wedge angle (of the cutting edges) must be at least or greater than 90. An acute angle extends the cutting path unnecessarily which leads-not only to an increase in the throw of the displaced cutting part-but also to a pulling effect on the hair being cut during the cutting operation, which can also cause skin irritation.

It is clear from what is stated hereinabove why a cutting guide plate cannot be used which has rhombic holes Whose greater axis lies approximately in the direction of movement of the cutter head; as with other tetragonal holes the opening ratio is favourable with this arrangement, but the skin protrusion in the rhornbic holes is nonuniform and the long cutting path irritates the hair roots, so that a plate having holes of this shape is rather bad than good in its results.

The cutting guide plate according to the invention does not have the drawbacks of known plates and also provides a particularly favourable relation between parameters of hole shape, hole size and arrangement, so that a dry shaving apparatus so provided has optimal cutting efiiciency. The perforations in the outer or guide plate are hexagonal and are so disposed that they have main diagonals alined with the direction of movement of the inner cutting plate, and the sides of these hexagonal perforations, considered in the direction of movement of the inner cutting plate, are rectilinear, i.e. non-angled, and extend parallel to the said main diagonals. In this way there is no gusset formed at these rectilinear sides of the perforations and at the two ends of the latter are located the desired wedgeshaped (angled) cutting edges having a wedge angle of at least 90; at the same time the rims of the perforations are of such shape as to permit satisfactory protrusion of the skin.

A regular hexagon shape is preferable because: it very nearly approaches the optimal circular hole shape. The hexagon shape has the additional advantage that it provides the most favourable opening ratio of all possible hole shapes. In the case of circular holes (through which the hairs pass) the opening ratio is-as stated hereinabove-smaller on account of the 'web gussets in that of tetragonal holes positioned diagonally-this being the critical case of rhomboids-the optimum is not obtained because the angles of such a hole which lie on the diagonal located vertically to the cutting direction form hole gussets which do not form part of the useful hole surface area.

In the case of shaver heads having a perforated plate as lower cutting element or knife, the holes in the cutter plate have hitherto been either longitudinal slots of substantially greater dimensions than the holes of the cutting guide plate, or they have had the same shape, size and arrangement thereas. According to the invention preference is also given to the last form of construction.

Independently of this it is also possible-according to a further feature of the invention and employing its basic inventive idea-to provide the cutter plate with rhomboid holes which, as already mentioned hereinabove, are already known insofar as type and arrangement are con cerned. The acute wedge angle is notas in the case of the cutting guide platea disadvantage, but onthe contrary is advantageous because the hair supported by a cutting edge of the cutting guide plate cannot be pulled; the pulling out is used without the hair being able to turn in the cutter plate during shaving, as occurs with hitherto known hole shapes.

This distinguishing features and advantages of the invention are further explained hereinafter with reference to the accompanying drawings which show different hole assemblies in diagrammatic section.

In these drawings:

FIGURES 1 and 2 show the cutting operation with a a perforated outer plate having cutting edges arranged in wedge relationship.

FIGURES 3 and 4 the effect of the wedge angle on the cutting path is shown.

FIGURES to 7 relative opening ratios in the case of circular, tetragonal and hexagonal holes,

FIGURE 8 shows the efiect of rhonrboid holes with inner cutter plates, and

FIGURE 9 shows the superposition of a hexagonal hole in an outer perforated plate to a rhomboidal hole in an inner reciprocable cutting part.

In FIGURES 1 and 2 is shown, greatly enlarged, the part of the hole of a perforated platethrough which hole the hair penetrateswhich is concerned in the cutting action; this hole is designated l, a cutter of the movable cutting system in the shaving head is designated 2 and is viewed from above, while 3 indicates the crosssection of a hair. In FEGURE 1 the movement is shown wherein the hair 3 is pressed against the two cutting edges 4, located in a wedge relationship to one another, by

the cutter 2 moved in the direction of the arrow 5; this starts the cutting operation. In FEGURE 2 the hair is almost out through and the cutting edges 4 carry out a pulling out.

From FIGURES 3 and 4 can be seen the unfavourable influence exercised by an acute wedge angle on the cutting path s.

In FIGURES 5, 6 and 7 are shown, enlarged to a lesser extent than in the previous figures, parts of the hole assemblies of different cutting guide plates; these plates are shown with circular holes 6 (FIGURE 5), with tetragonal holes 8 (FIGURE 6); and with the hexagonal holes 19 assembled according to the invention (FIGURE 7). The direction of movement of the cutters is again shown by arrows 5. In FIGURE 5 can be seen the gusset formation 7, indicated by hatching, in the webs of the hole assembly, and in FIGURE 6 the gusset formation 9 in the angles (or tetragonal holes 8 of the hole assembly) not acting as wedge-shaped cutting edges. .111 FIGURE 6 the outline of a hair 3 is shown in broken line in its two possible extreme positions in a tetragonal hole 8. In the case of an assembly of hexagonal holes there is no gusset formation, and the opening ratio is optimal, this being clearly visible from the position of the hair 3 in FIGURE 7. the sides of the hexagonal holes 10 considered in the direction of movement 5 are rectilinear, i.e. non-angled, thus permitting the avoidance of the gusset in the corners 9 shown in FIGURE 6. The two ends of the hexagons are angled and have Wedge angles of at least 90. The hexagonal holes of FIGURE 7 have main diagonals alined with the direction of movement 5 of the inner cutter plate; the rectilinear sides of the hexagonal holes are substantially parallel with these main diagonals.

FIGURE 8 shows a single hole 1 of a cutter plate 12 moved in the direction of the arrow 5; said cutter plate In FIGURE 7 13 with hexagonal holes 10 whose main diagonal is alined has rhomboid holes and a hair 3 is shown passing through said single hole 1. The wedge-shaped hole edges permit a pulling out and so grip the hair that it cannot turn, during the cutting operation, in either direction of the double arrow 11; such a turning action can, like a pulling action on the hair of persons with sensitive skins, cause irritation of the hair roots.

In FIGURE 9 is shown an outer perforated cutter plate with the direction of movement indicated by double arrow 5of an inner cutting plate 12 which has themboidal holes; the main diagonal of rhomboidal holes 1 is also alined with the direction of movement of the inner cutting plate 12.

The invention is not restricted to perforated plates with regular hexagonal holes or to shaver heads having cutter parts which oscillate and which in particular move in the longitudinal direction, whether. said cutter parts are individual cutters, cutter heads or cutter plates. The hole shapes according to the invention can also be used in combination with other known hole shapes. Thus it can be expedient to provide known longitudinal slotswhich are favourable for cutting through longer hairs on the outer edge of a cutting guide plate, and to provide holes in the centre of the hole assembly in the plate.

I claim:

1. In a dry shaver cutting head, comprising an outer flexible perforated cutter plate and an inner reciprocable cutting part arranged to severe beard hairs protruding inwards through the perforations in the outer cutter plate, the improvement that the perforations in the outer plate are hexagonal and have main diagonals alined with the direction of movement of the inner cutting part.

2. The structure as set forth in claim 1 in which the inner cutting part is a flexible plate of rhomboidal holes arranged to cooperate with the hexagonal holes in the outer cutter plate, the main diagonals of the rhomboidal holes in the inner flexible plate being alined with the direction of reciprocation of the inner flexible plate.

References Cited in the file of this patent UNITED STATES PATENTS 2,141,582 Wimberger Dec. 27, 1938 2,198,833 Muras Apr. 30, 1940 2,249,825 Hanley July 22, 1941 2,251,577 Rand Aug. 5, 1941 2,341,665 Scully Feb. 15, 1944 2,573,758 Bailey Nov. 6, 1951 2,900,719 Kohner et al Aug. 25, 1959 FOREIGN PATENTS 663,487 Germany Aug. 6, 1938 64,863 Norway May 26, 1942 1,143,839 France Apr. 15, 1957 1,196,220 France May 25, 1959 

1. IN A DRY SHAVER CUTTING HEAD, COMPRISING AN OUTER FLEXIBLE PERFORATED CUTTER PLATE AND AN INNER RECIPROCABLE CUTTING PART ARRANGED TO SEVERE BEARD HAIRS PROTRUDING INWARDS THROUGH THE PERFORATIONS IN THE OUTER CUTTER PLATE, THE IMPROVEMENT THAT THE PERFORATIONS IN THE OUTER PLATE ARE HEXAGONAL AND HAVE MAIN DIAGONALS ALINED WITH THE DIRECTION OF MOVEMENT OF THE INNER CUTTING PART. 